The present exemplary embodiments relate generally to ophthalmic examination systems. In one particular application, an interface device is utilized to facilitate communication between a refraction system and a display within the ophthalmic examination system. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
An eye examination is a battery of tests performed by an optometrist or ophthalmologist to assess a subject's vision and ability to focus on and discern objects. An automated ophthalmic exam system can be employed to aid in the determination of a subject's refractive error and to identify an appropriate lens prescription to correct such error. In one example, an automated ophthalmic system includes a phoroptor and an eye chart. The phoroptor is used to present powered lenses in front of a subject's eyes. The eye chart can be read by the subject via the phoroptor to aid in the determination of visual acuity during the test.
The phoroptor can be employed to refine the prescription, identified via the autorefractor, to one which provides the subject with the best vision. The lenses within a phoroptor refract light in order to focus images on the subject's retina. By changing these lenses, the examiner is able to determine the spherical power, cylindrical power, and/or cylindrical axis necessary to correct a subject's refractive error. From the measurements taken, a corrective lens prescription can be identified that contains at least six numerical specifications (three for each eye): sphere, cylinder and axis.
An eye chart is used to measure visual acuity when viewed by the subject via the phoroptor. Types of eye charts can include a Snellen chart, a tumbling E chart, and a Landolt C chart. Charts usually display several rows, wherein each row contains different sized test symbols or optotypes. The subject is asked to identify the optotypes on the chart, usually starting with large rows and continuing to smaller rows until the optotypes cannot be reliably identified any longer. Charts can be employed with very young children or illiterate adults that are incapable of letter recognition. One version uses simple pictures or patterns (e.g., an apple, a house, a square, and a circle) that are selected based upon the results of recognition trials. The tumbling E chart has the block letter “E” turned in different orientations, wherein the subject simply indicates which direction each “E” is facing. Similarly, the Landolt C chart has rows of circles with different segments missing and the subject describes where each broken piece is located.
Eye charts can be presented via a computer-based display and/or a chart projector in concert with the refraction system. There are several potential advantages such as more precise measurement and less examiner induced bias in the examination. Compatibility issues can arise, however, when communication is attempted between a refraction system and a computer-based eye chart produced by disparate manufacturers. In particular, automated ophthalmic exam systems generally employ proprietary protocols to communicate between such components. Accordingly, systems and methods are needed to facilitate communication between automated ophthalmic exam system components, regardless of the manufacturer.